U.S. Pat. No. 4,643,876 discloses a sterilization system in which an agent such as hydrogen peroxide is introduced into an evacuated sterilizing chamber wherein it is vaporized and allowed to disperse onto the items to be sterilized. After a desired period of time, electrical energy is then applied in the chamber to ionize the gas to form a plasma at a power level sufficient to achieve sterilization. These steps can be performed in different chambers.
The system is proving to be very effective, and also has a number of advantages over other known systems. Consequently, the system is being commercialized and a need exists for apparatus providing the proper quantity of the desired fluid in a safe, convenient and practical manner. Also, an injection system must perform its function accurately and reliably without providing a leak path for the introduction of unwanted air or other material to the sterilizing chamber. In addition to preventing leaks, the accuracy requirement includes the need for minimizing the volume of fluid that remains in the system between injections.
When the system is used with sterilizing apparatus in a medical environment such as in a hospital, it is likely to be operated on a repeated basis throughout the day by personnel having a widely varying range of understanding of the apparatus employed. Hence, it is important that the system be simple to operate, be fully automated and have adequate safeguards with respect to human error in view of the critical nature of sterilization of medical items. Minimizing the chance of human error is thus important. Also, the apparatus must have adequate reliability for heavy usage of the apparatus over an extended period of time.
Prior fluid injection systems in sterilizing apparatus do not provide the desired features. In one known system, ethylene oxide gas is sealed under its own pressure in a container and then dispensed as needed. This approach is not practical with a liquid delivery system in that a gaseous propellant contained in the liquid is not acceptable in the sterilizing process. Also, delivery pressure decays during the delivery process, which can result in an undelivered dead volume, and degradation in the quality of atomization of the fluid as it enters the chamber.
Thus, a need exists for an improved system.